* tree-ssa-dom.c (thread_across_edge): Do not thread jumps if a

	PHI argument is set from a PHI_RESULT in the same block and the
	PHI argument is not the same as the PHI result.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@92102 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 10 insertions, 0 deletions

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 3a3bdada4d8..81fdb0e8652 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -550,6 +550,16 @@ thread_across_edge (struct dom_walk_data *walk_data, edge e)
     {
       tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
       tree dst = PHI_RESULT (phi);
+
+      /* If the desired argument is not the same as this PHI's result 
+	 and it is set by a PHI in this block, then we can not thread
+	 through this block.  */
+      if (src != dst
+	  && TREE_CODE (src) == SSA_NAME
+	  && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
+	  && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
+	return;
+
       record_const_or_copy (dst, src);
       register_new_def (dst, &block_defs_stack);
     }